Devoxx 2013: The Modular Java Platform and Project Jigsaw

Mark Reinhold

Java platform layers; total of 54 mb:

• compact 1: 11mb: core
• compact 2: 16mb (Jdbc, rmi, jaxp,...)
• compact 3: 30mb (rowset, jdbc, prefs, xmldsig)
• 54mb: javafx, crypto, httpservers, corba...
• + extra tools (jaxws, devtools,...)

Not a perfect solution -> better to make a dependency model of each component (directed graph).

Performance solution needed for:

• fast class lookup
• aggressive inlining
• ahead of time compilation (startup speed)
• JVM-specific memory images
• removal of unused fields/methods/classes

Solution:Jlink (optional tool)

• input: *.jar, *.class, *.jmod
• output: jmod, jar, JVM image
• e.g.:
  • jlink -mods javafx,rmi,nashorn -d $JRE
  • javac -mods javafx,rmi,nashorn -d classes *.java
  • java -mods javafx,rmi,nashorn -jar ...
• requires changes to the Java Runtime: no rt.jar & tools.jar anymore (bad representation for JVM)

Security & modularity

• current setup can't hide some parts. E.g.: sun.misc.Unsafe
• historic checks: java.lang.SecurityManager::checkPackageAccess: no static checks possible
• modules & dependency graph can help validate access to sensitive packages
• some internal packages will be removed -> must be fixed!:
  • sun.*
  • *.internal.*